Is there a specific size...like...mb wise that it has to be under? I didn't see anything like that when looking through JFC's announcment....he mentions that animated GIFs be kept to 1.5mb...so I was just wondering if its that way for rotating sigs too, or if I could just have three different 500x165 banners?

Faded, if you want to do a rotating sig like mine, just make sure that all of the banners fit within the guideline specs. To get them to rotate you actually use an outside source/website that generates the code to get them to rotate and just post the link.

RandomSigs.com is a really easy one to use. You just UL your pics onto it and it provides you with the link to put in your sig.